The invention relates, in general, to metal forming and, more particularly, to a multiple-mandrel ring rolling machine for hot rolling rings of a small to medium diameter, for example, roller bearing rings.
German Pat. No. 438,542 discloses machines where the main roll is mounted immovably in the rolling machine frame. The roll mandrels, disclosed therein, are mounted laterally of the main roll in overhung position in a rolling platform either rotating in a rolling machine frame or movable on a rolling machine frame. The roll mandrels can be brought successively into rolling position by rotation or displacement, or can be fed to the main roll and removed from the latter.
German Pat. No. 703,436 discloses a multiple-mandrel ring rolling machine having a support for the mandrel roll axle, on both sides thereof, in a rolling platform arranged laterally of the main roll. An automatic stripping of the finished-rolled ring from the rolling platform is made possible, in this way, so that the mandrel rolls, due to the two-part design of the mandrel roll axle, can be lifted upward from the rolling platform, and a stripper pushes the finished rolled ring from the rolling platform.
In addition, a multiple mandrel ring rolling machine, disclosed in German Pat. No. 1,098,481 has a rolling platform for carrying the mandrel rolls which is mounted for rotation about the main roll.
These known multiple-mandrel ring rolling machines, which are effective as far as the number of rings produced is concerned, generally have drawbacks. A reliable automatic change of the workpieces, which is highly desirable for maximizing the output of the machines, is impeded by the fact that the rolling platform having the mandrel rolls can either only stand still for a very short time because of the necessary cycles required for machining the rings, or runs continuously, though at a reduced speed. In addition, the mandrel rolls, which are mounted with a split axle in the interest of a rapid change of the workpieces, as well as the mandrel rolls mounted unilaterally or in overhung position, lack the rigid support necessary for obtaining precision ring dimensions so that considerable deviations from the nominal values, depending on the variable factors affecting the use, must be acceptable in the rings produced on these ring rolling machines. Moreover, the semi-automatic change of workpieces in these machines requires a great engineering effort and large revolving masses, while the machines show little functional clarity and are not easily accessible, so that they are on the whole not suitable for high demands regarding accuracy to the form and measure of the rings with short cycle times. Furthermore, the mandrel roll is fed, in the known multiple-mandrel ring rolling machine, relative to the main rolls by a fixed amount normally determined by the rotation of the rolling platform. This does not permit rapid and automatic corrections so that the diameters of the finished rings vary within the volume of the ring blanks used. Finally, the use of axial rolls requires, in multiple-mandrel ring rolling machines of the known type, a great expenditure of effort for achieving the vertical calibration of the rings so that utilizing this possibility to increase quality had to be foregone in the past.